Electro Industries Nexus 1262, Руководство по установке и эксплуатации

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e Electro Industries/Gauge Tech
Doc # E151701
5-4
For All RS485 Connections:
Use a shielded twisted pair cable 22 AWG (0.33 mm
2
) or larger, grounding the shield at one end
only.
Establish point-to-point configurations for each device on a RS485 bus:
Connect (+) terminals to
(+) terminals; connect (-) terminals to (-) terminals.
Protect cables from sources of electrical noise.
Avoid both “star” and “tee” connections (see Figure 5.6).
No more than two cables
should be
connected at any one point
on an RS485 network, whether the
connections are for devices, converters or terminal strips.
Include all segments when calculating the total cable length of a network. If you are
not
using an
RS485 repeater, the maximum length for cable connecting all devices is 4000 feet (1219 meters).
For an
RS485 Daisy Chain
connection, in which you link
multiple devices in a series
, connect
shield to RS485 Master and individual devices as shown in Figure 5.5. You may also connect the
shield to earth-ground at one point.
RS485 communication allows multiple devices to communicate on a bus. The Meter’s Port 1 and
Port 4 are RS485 terminals, viable for a distance of up to 4000 feet (1219 m). Below is a detail of a
2-wire RS485 port.
Figure 5.4: 1262/1272 2-Wire RS485 Port Detail
Meter
2-wire RS485 Port